This invention relates to a safety device for a fluid hose having at one end a separable connector.
The safety device of the present invention is particularly applicable to liquid fuel dispensing hoses, as used for example on garage forecourt fuel pumps. However, the invention may be used in other areas of industry where a flexible hose is used to dispense a liquid or gas to a movable item, such as a vehicle, a container, or the like. Thus, though in the following the invention will primarily be described with reference to its use for forecourt fuel pumps, nevertheless it is to be understood that the invention is not limited to that use.
A recognised problem with a garage forecourt fuel pump having a flexible hose fitted at its free end with a dispensing nozzle incorporating a control valve is that the hose can become damaged, so leading to a loss of fuel which is both a fire risk and an environmental hazard. One fairly common source of such hose damage is when a motorist, on completing the filling of his vehicle's fuel tank, then drives off leaving the dispensing nozzle still in the filler pipe of the vehicle. A similar problem can arise with L.P.G. where the nozzle is physically connected to a vehicle's filler pipe.
In an attempt to minimise the damage to both the hose and the pump, and also to minimise the loss of fuel, it is known to fit a forecourt fuel pump hose with a two-part connector which automatically separates when the hose is subjected to a tensile load above some pre-determined level. The two parts of the connector both include spring-loaded non-return valves which automatically close on the connector separating under an applied tensile load, so as to prevent any loss of fuel from the fuel pump side, bearing in mind that the pump might still be running, as well as from the part of the hose downstream of the connector. Such connectors may be provided between a rigid pipe associated with the fuel pump and the flexible hose, partway along the length of the hose, or at the dispensing nozzle, to connect the hose to the nozzle.
Though a two-part connector of the kind described above can significantly reduce the fire risk and pollution risk caused by a motorist driving away whilst the dispensing nozzle is still located in the fuel filler pipe of his vehicle, it is found that if the connector is to stay connected for all normal usage of the fuel pump, the tensile load required to separate the connector under emergency conditions must be set relatively high. In that case, considerable energy will be stored in the flexible hose by the tensile load applied to that hose at the point at which the connector parts separate. This stored energy, on being released on separation of the connector parts, can do considerable damage to the fuel pump or the vehicle, depending upon the location of the connector. For example, if the connector is at the upstream end of the flexible hose, to connect that hose to a rigid pipe of the fuel pump, then the upstream end of the hose together with its connector part can snake back to the vehicle, and cause significant damage to the vehicle. Conversely, if the connector is at the dispensing nozzle end, the free end of the hose can spring back towards the pump and cause damage there. Further, in either case, persons standing nearby can be hit by the hose, moments after the connector separates.